1. Field of the Invention
The present invention generally relates to video signal duplicating systems in which a video signal is reproduced from a first record medium and a reproduced video signal is recorded on a second record medium. More particularly, this invention relates to a video signal duplicating system in which a video signal is duplicated at a speed higher than the normal playback speed.
2. Description of the Related Art
When a video information such as a movie or the like is reproduced from a video tape and then recorded on another video tape, a playback video tape recorder (VTR) and a recording VTR are both driven at a speed, for example, which is twice as high as the normal speed and a twice normal speed reproduced signal is input to the recording VTR in order to reduce the duplicating time. A twice normal speed reproduced signal has a rate which is twice the normal rate, that is, its timebase is compressed by 1/2.
As a method for obtaining the twice normal speed reproduced signal from the playback VTR, the following two methods (1) and (2) have been proposed. In the method (1), both a transport speed of a video tape (record medium) and a driving speed of a reproducing system such as a rotary head drum or the like are increased to twice normal speed, and according to the method (2), the number of playback heads mounted on the rotary head drum is increased to twice the normal number.
However, according to the method (1), a revolution rate of a rotary head is considerably increased. For example, in a video tape recorder of D2 type described in U.S. Pat. No. 5,012,361, the revolution rate of the rotary head reaches 10800 r.p.m. so that, in actual practice, various technical problems must be solved. Furthermore, since a signal of twice the normal frequency band is delivered from the playback head, the signal processing system of the existing video tape recorder must be modified greatly.
The method (2) needs a special rotary head drum and a special playback head and also needs two signal processing systems, which requires the existing video tape recorder to be modified greatly.
Therefore, in accordance with the methods (1) and (2), the development period of the video tape recorder is extended and the development cost or the like also is increased. In addition, the methods (1) and (2) cannot satisfy the user's requests in the early stage.